Insulin is widely used as an effective therapeutic drug for the treatments of type 1 and type 2 diabetes mellitus. The side effect of insulin in type 2 diabetes is that it may cause hypoglycemia. Another common used prescription drug for type 2 diabetes is gliclazide. This drug is as effective as insulin, but it may cause the side effect in enteron. It is extremely important to develop a novel safe and effective therapeutic drug for type 2 diabetes. Recently, research from pharmaceutical companies and many institutions demonstrated that glucagon-like peptide-1 (GLP-1) is an excellent therapeutic target for type 2 diabetes. GLP-1 can promote the secretion of insulin and enhance its sensitivity. Furthermore, treatment of type 2 diabetes patients with GLP-1 does not lead to hypoglycemia. More recent studies showed that GLP-1 is effective for both type 1 and type 2 diabetes mellitus. The latest research status of glucagon-like peptide-1 and its receptors is reviewed.